A Blue-Purple Pigment-Producing Bacterium Isolated from the Vezelka River in the City of Belgorod

Some novel bioactivities of Virgibacillus halodenitrificans carotenoids, isolated from Wadi El-Natrun lakes

Carotenoids come in second among the most frequent natural pigments and are utilized in medications, nutraceuticals, cosmetics, food pigments, and feed supplements. Based on recent complementary work, Virgibacillus was announced for the first time as a member of Wadi El-Natrun salt and soda lakes microbiota, identified as Virgibacillus halodenitrificans, and named V. halodenitrificans DASH; hence, this work aimed to investigate several in vitro medicinal bioactivities of V. halodenitrificans DASH carotenoids. The carotenoid methanolic extract showed antioxidant activity based on diphenylpicrylhydrazyl (DPPH) scavenging capacity with a half-maximal concentration (IC50) of 1.6 mg/mL as well as nitric oxide (NO) scavenging action expressed by an IC50 of 46.4 µg/mL. The extract showed considerable inhibitory activity for alpha-amylase (α-amylase) and alpha-glucosidase (α-glucosidase) enzymes (IC50 of 100 and 173.4 μg/mL, respectively). Moreover, the extract displayed selective anticancer activity against Caco-2 (IC50 = 138.96 µg/mL) and HepG-2 cell lines (IC50 = 31.25 µg/mL), representing colorectal adenocarcinoma and hepatoblastoma. Likewise, the extract showed 98.9 % clearance for human hepatitis C virus (HCV) using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), HCV-NS5B polymerase activity inhibition (IC50 = 27.4 µg/mL), and selective inhibitory activity against human coronavirus (HCoV 229E) using the plaque reduction assay (IC50 = 53.5 µg/mL). As far as we can tell, the anticancer, antiviral, and antidiabetic attributes of Virgibacillus carotenoids are, de novo, reported in this work which accordingly invokes further exploration of the other medicinal, biotechnological, and industrial applications of Virgibacillus and haloalkaliphilic bacteria carotenoids.

Sensitivity of Janthinobacterium Lividum to Low Concentrations of Hydrogen Peroxide and the Effect of Mild Oxidative Stress on Pigment Yield

In the course of assessing the sensitivity of the Janthinobacterium lividum VKM B-3515 strain to low concentrations of hydrogen peroxide, it was found that at a content of 0.003% H2O2, the growth properties of the bacterium during submerged cultivation without pigmentation differed statistically insignificantly relative to the control variant at 16 hours of incubation and beyond. Whereas in the presence of peroxide at 12 hours the optical density was lower than in the control by 97%. When cultivating by the surface method, the respiration intensity did not significantly differ between the control and experimental variants. However, during the extraction of the pigment, it was found that in the presence of hydrogen peroxide, the optical density of the acetone extract significantly exceeds the control variant by 28%. It can be assumed that, at the same growth parameters of the culture, the biosynthesis of violacein is stimulated and the population can adapt to the peroxide content, and the peroxide concentration itself decreases due to the cost of catalytic reactions. Further studies of the sensitivity of J. lividum VKM B-3515 to various oxidizing agents will allow us to consider the effect of weak oxidative stress on the biosynthesis of violacein.

Natural Substrates and Culture Conditions to Produce Pigments from Potential Microbes in Submerged Fermentation

Pigments from bacteria, fungi, yeast, cyanobacteria, and microalgae have been gaining more demand in the food, leather, and textile industries due to their natural origin and effective bioactive functions. Mass production of microbial pigments using inexpensive and ecofriendly agro-industrial residues is gaining more demand in the current research due to their low cost, natural origin, waste utilization, and high pigment stimulating characteristics. A wide range of natural substrates has been employed in submerged fermentation as carbon and nitrogen sources to enhance the pigment production from these microorganisms to obtain the required quantity of pigments. Submerged fermentation is proven to yield more pigment when added with agro-waste residues. Hence, in this review, aspects of potential pigmented microbes such as diversity, natural substrates that stimulate more pigment production from bacteria, fungi, yeast, and a few microalgae under submerged culture conditions, pigment identification, and ecological functions are detailed for the benefit of industrial personnel, researchers, and other entrepreneurs to explore pigmented microbes for multifaceted applications. In addition, some important aspects of microbial pigments are covered herein to disseminate the knowledge.

Molecular signatures of Janthinobacterium lividum from Trinidad support high potential for crude oil metabolism

Background

Janthinobacterium lividum is considered to be a psychrotrophic bacterial species. For the first time in the literature, J. lividum strains were isolated from Trinidad presenting with atypical features - hydrocarbonoclastic and able to survive in a tropical environment.

Methods

Identification of the Trinidad strains was carried out through 16S rRNA phylogenetic analysis. Gene-specific primers were designed to target the VioA which encodes violacein pigment and the EstA/B gene which encodes secreted extracellular lipase. Bioinformatics analyses were carried out on the nucleotide and amino acid sequences of VioA and EstA/B genes of the Trinidad Janthinobacterium strains to assess functionality and phylogenetic relatedness to other Janthinobacterium sequences specifically and more broadly, to other members of the Oxalobacteraceae family of betaproteobacteria.

Results

16S rRNA confirmed the identity of the Trinidad strains as J. lividum and resolved three of the Trinidad strains at the intra-specific level. Typical motility patterns of this species were recorded. VioAp sequences were highly conserved, however, synonymous substitutions located outside of the critical sites for enzyme function were detected for the Trinidad strains. Comparisons with PDB 6g2p model from aa231 to aa406 further indicated no functional disruption of the VioA gene of the Trinidad strains. Phylogeny of the VioA protein sequences inferred placement of all J. lividum taxa into a highly supported species-specific clade (bs = 98%). EstA/Bp sequences were highly conserved, however, synonymous substitutions were detected that were unique to the Trinidad strains. Phylogenetic inference positioned the Trinidad consensus VioA and EstA protein sequences in a clearly distinct branch.

Conclusions

The findings showed that the primary sequence of VioAp and EstA/Bp were unique to the Trinidad strains and these molecular signatures were reflected in phylogenetic inference. Our results supported chemotaxis, possible elective inactivation of VioA gene expression and secreted lipase activity as survival mechanisms of the Trinidad strains in petrogenic conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02346-4.